This invention relates to processes for creating and inspecting semiconductor devices and, more particularly, to an immersion type optical system for lithographically printing patterns and for inspecting patterns.
Generally both optical lithography and inspection are performed today by illuminating the surface of the semiconductor wafers while the wafer is immersed in a gas at ambient pressure. Some defect examinations might use oil immersion microscopy. To obtain greater resolution, alternative techniques are under development including electron beam illumination, x-ray illumination, and ion beam illumination.
U.S. Pat. No. 5,121,256 discusses placing a solid immersion lens in proximity to a wafer, while the wafer itself is maintained in air at ambient pressure. U.S. Pat. No. 5,610,683 proposes immersing the wafer in a high index of refraction liquid.
Accordingly, it is an object of the invention to provide an improved method of optical lithography, wherein the method employs a super-critical fluid as an immersion medium.
It is another object of the invention to proved an improved method of optical inspection, wherein the method employs a super-critical fluid as an immersion medium.